Reaming apparatus



Feb. 28, 1967 w. R. GARRETT ETAL 33 I REAMING APPARATUS Original FiledJan. 11. 1960 5 Sheets-Sheet 2 Qcrrref/ Feb. 28, 1967 w. R. GARRETT ETAL3,306,381

REAMING APPARATUS 5 Sheets-Sheet 4 Original Filed Jan. 11. 1960 II VUQQQOQQOA QOGO. O

GGQOQQAUO INVENTORJ ATTO/M/f) Feb. 28, 1967 w. R. GARRETT ETAL 3,306,381

REAMING APPARATUS 5 Sheets-Sheet 5 Original Filed Jan. 11. 1960/V////0/)7 Robe/z 50/7 9 2 f INVENTORS Jfow/e a 6'.

ATTORNEY United States Patent Ofifice 3,306,381 Patented Feb. 28, 19673,306,381 REAMING APPARATUS William Robert Garrett and Stanley C. Moore.Midland,

Tex., assignors to Drilco Oil Tools, Inc., Midland, Tex., a corporationof Texas Continuation of abandoned application Ser. No. 1,556, Jan. 11,1960. This application Dec. 16, 1963, Ser.

14 Claims. (Cl. 175-346) This application is a continuation of our priorcopending application Serial Number 1,556, filed January 11, 1960, nowabandoned in favor of this application.

This invention pertains to rotary drilling apparatus and moreparticularly to a reamer used above a drill bit for reaming the sidewalls of an earth bore.

According to the invention a reamer is provided including a tubular bodythreaded at its ends for insertion in a drill string between the bit anddrill pipe, normally just above the drill bit between the drill bit andlowest drill collar, although the reamer is also of use in otherlocations in the drill string.

The reamer body is provided with a plurality of rollers each havingsintered tungsten carbide inserts protruding therefrom disposed inannular rows of increasing diameter progressing upwardly.

OVERGAGE INSERTS The reamer radius, that is, the radius from the axis ofthe reamer body to the extremity of a carbide insert when its axis isaligned with a radius from the axis of the reamer body, at the uppermostrow or rows of inserts is larger than the radius of the full gage holethat is desired to be drilled. The inserts in each overgage row arespaced far enough apart so that by turning the rollers to a positionwhere no overgage insert projects straight out radially from the reameraxis the reamer can be moved axially through a full gage hole withoutobstruction. When the drill string is rotated these overgage insertswill underream the hole slightly and thus maintain it of at least fullgage until the overgage inserts are worn down below full gage.

TORQUE UP BANDS In certain embodiments of the invention on-gage hardfacing bands may be provided above the overgage inserts to indicate whenthe overgage inserts are worn down by causing high torque in the drillstring. Under-gage hard facing bands may be provided below the lowermostrow of inserts to indicate by torque-up when the drill below the reamerhas worn under gage to a predetermined amount.

OBLATE TIPPED INSERTS The outer ends of the inserts are preferablyrounded, e.g. hemispherical or approximately so, which has been found toprovide a maximum active area with a minimum of failure although othershapes may be used and an insert tip having an approximately truncatedhemispherical shape may be used with advantage.

BEARING SLEEVES In certain embodiments of the invention the rollers maybe provided with bearing sleeves and the inserts placed in radial holesextending clear through the roller bodies so that the inserts bottom onthe bearing sleeves, thereby facilitating assembly, increasing theroller life, and making possible the easy salvage of used inserts fromworn out reamers and rollers. The sleeved roller body construction makesit possible to provide both a very hard metal for the bearing shaftcontact area and hard tough metal for the roller body to retain theinserts despite the severe service.

For a detailed description of several preferred embodiments of theinvention reference will now be made to the accompanying drawingswherein:

FIGURE 1 is an elevation showing a reamer embodying the invention inconjunction with a per se conventional three cone rock bit to the top ofwhich the reamer is connected;

FIGURE 2 is a vertical section through one of the rollers of the FIGURE1 reamer, together with immediately adjacent portions of the rest of thereamer;

FIGURES 3, 4 and 5 are horizontal sections taken on lines 33, 44, and5-5 of FIGURE 2;

FIGURE 6 is a view similar to FIGURE 5 with the roller turned so as topass through a full gage hole;

FIGURE 7 is a vertical section through another form of reamer rollerembodying features of the invention;

FIGURE 8 is a horizontal section taken on line 88 of FIGURE 7;

FIGURE 9 is a flat layout of the outer surface of the roller of FIGURES7 and 8;

FIGURE 10 is a vertical section through another form of reamer rollerembodying features of the invention; and

FIGURE 11 is an axial section through the outer end of a roller insertshowing to an enlarged scale the shape thereof according to the FIGURES16 embodiment of the invention.

REAMER AND DRILL BIT ASSEMBLY Referring now to FIGURE 1 there is shown athree cone rock bit 20 to the upper end of which is connected a reamer21 embodying the invention. The reamer includes a tubular body 22 havinga threaded pin 23 at its upper end and a threaded socket at its lowerend for engagement with the rock bit pin.

The reamer body 22 is recessed to accommodate a plurality, e.g., three,rollers such as 30 (see also FIG. 2) each adapted to rotate on shaft 31.The lower end of shaft 31 is mounted in an apertured block 32. As bestseen in FIGURE 3 the block is dovetailed into the reamer body and has aslot 34 in its lower end to receive the flattened end 35 of the shaft31, thereby preventing the shaft from turning. Apertured block 36 (seeFIG. 4) is dovetailed into the reamer body 22 to receive the upper endof shaft 31. Referring again particularly to FIG- URES 1 and 2, a pin 37holds the block 36 against vertical motion and likewise prevents axialmotion of shaft 31.

REAMER ROLLER Still referring to FIGURES 1 and 2, the lower outer edgeof the roller is bevelled at 38 and the outer peripheral surface ofroller 30 is stepped providing six annular lands 39A, 39B, 39C, 39D, 39Eand 40. Disposed respectively on the lands 39A-E are five annular rows41, 42, 43, 44, 45 of tungsten carbide inserts. Each row of insertsprojects at least as far and preferably 'a little farther radially thanthe'roller land just above it, thereby protecting such land againstundercutting during use.

Thus, when the roller is turned to place one of the apertures or holes57 (infra) receiving the inserts 58 (infra) into 'a position where suchaperture, and the insert therein, are at a maximum distance from thereamer axis where the insert can perform its reaming function, thedistance from the outermost tip of the insert to the reamer axismeasured perpendicular to the reamer axis is at least as great as thedistance from the reamer axis of the portion of the outer surface of theroller, i.e., the land, adjacent the aperture nearest thereabove.Compared to the diameter of the full gage hole 46 that is drilled bydrill bit 20 when it is new, the reamer radius at rows 41, 42, and 43 isundergage but of progressively larger radius going up the roller. Insertrow 44 is on gage. Insert row 45 is over gage.

Hard facing bands 46, 47 at the upper end of each roller are on gage.Hard facing band 48 at the lower part of each roller is a predeterminedamount undergage, and hard facing band 49 is provided on the bevelledguide shoulder at the lower end of each roller. No hard facing is neededon the upper guide bevel 50.

The hard facing can be applied to the roller body surface, or as shown,to annular grooves formed therein. The hard facing may be tube metal(crushed cast tungsten carbide in a tubular steel jacket) welded inplace on the roller body. If, as shown, the hard facing is flush withthe roller surface, it will be apparent that upper land 40 which carrieson gage bands 46, 47 will itself be on gage.

As shown in FIGURE 2, each roller 30 comprises a body 55 of tough steel,ductile enough to take shocks without cracking but hard enough, e.g.25-30 Rockwell C scale, to wear well under abrasive service. For exampleA181 8620 may be used. Press fitted into each roller body is a sleeve orbushing 56 of some hard steel such as high chrome bearing steel, ATS52100 series, carburized stainless steel, or rock bit bearing steel. Ahardness of 58-65 Rockwell C scale is appropriate.

CARBIDE INSERTS Holes such as 57 are bored in roller body 55 to receiveinserts 58 that make up the rows 41-45. The inserts are made of sinteredtungsten carbide and are of generally cylindrical shape with preferablyhemispherical outer or cutting ends. The inner ends are bevelled asshown at 59, to facilitate insertion into the holes 57, there being amechanical interference or press fit of the order of one to threethousandths of an inch diameter difference. The inserts may be of theorder of 7 inch, or preferably 1 inch in diameter. In order that all theinserts can bottom on the same uniform diameter sleeve 35 they arenecessarily of different lengths, the inserts in the overgage row beinglongest. The drawing, being to scale, shows the various lengths of theinserts. The shortest inserts penetrate the sleeve a distance greaterthan their diameters. The inserts protrude beyond the outer periphery ofthe roller about inch.

The spacing of the inserts as measured around the periphery of theroller may be of the order of one inch apart on centers. The inserts ineach row, though shown in FIGURE 2 by draftsmans license as being inregister with those in adjacent rows, are preferably staggered so thatonly the inserts in every other row are in register and those in rows inbetween are circumferentially disposed half way between the inserts inadjacent rows. This increases the minimum distance between holes andstrengthens the roller. With the aforementioned one inch spacing of theinserts in the roller, even with inserts of =7 inch diameter the spacingbetween the nearestside surfaces of the protruding ends of adjacentinserts is at least as great as the diameter of the inserts. This istrue not only of adjacent inserts in the same row but in adjacent rows.In this regard see also the layout of another embodiment of theinvention shown in FIGURE 9 and described later on herein.

The inserts in the over gage row or rows usually will be somewhatfatrher apart, and if more than one row is used the inserts in each rowwill be in circumferential register with those in adjoining rows. Thisarises from the requirement that the roller can be turned to a positionin which the greatest radial extent of any part of the roller from thereamer axis is no greater than the radius of a full gage hole.

OVERGAGE REAMING Referring now to FIGURES and 6, there is shown thecircumferential disposition of the eight on gage inserts 44-1 44-8, andthe six over gage inserts 45-1 45-6. In FIGURE 5 the roller 30 is turnedso that over gage insert 45-1 is aligned radially with a reamer radiusand therefore protrudes a maximum amount from the reamer to cut anovergage hole. In FIGURE 6 on gage insert 44-8 is shown aligned with areamer radius and hence in position to cut an on gage hole, while thebisector of the angle between overgage inserts 45-1 and 45-6 is alignedradially with a reamer radius and in this position the inserts do notprotrude beyond the gage radius of the hole.

It will be understood that during drilling a new drill bit willinitially cut a full gage hole and the over gage row of inserts willenlarge the hole to slightly over gage. The drill bit will wear fasterthan the reamer and as the drill bit becomes under gage the on gageinserts of the reamer will enlarge the hole to full gage and the overgage inserts will enlarge it still more. The hard facing bands 46, 47will burnish the hole. When the bit becomes worn down still more theunder gage rows on the reamer will come into action and enlarge the holesome in advance of the on gage row of inserts. The hard facing band 49will protect the under side of the rollers from Wearing away rapidly.The on gage inserts may be worn slightly undergage by this time but theovergage row of reamer inserts will enlarge the hole still farther tosomewhat over gage. However the over gage inserts will also be wornsomewhat by this time so that the hole radius will not be as large aswhen drilling with the new hit and reamer commenced. Therefore althoughthe hole is still overgage at all points it is not of uniform radius.

Finally, when the bit and reamer wear down still farther, one of twothings happens to warn the operator it is time to change tools. If thebit wears down to the diameter of hard facing band 48, the drill stringtorque will increase; if the reamer wears down to the point where overgage inserts 45 extend no farther radially than hard facing bands 46,47, the drill string torque will increase; in both cases the torqueincrease is due to the engagement of the hard facing bands with the wellwall. When the drill string torque is increased, the drill string isremoved from the well and the bit or reamer or both replaced as need be.

During removal of the drill string for tool replacement, and duringreplacement of the drill string into t-he hole with new tooling, it isnecessary for the over gage inserts to move axially up and down the holewhich in some places may be no more than full gage in radius. This ispossible by the rollers turning to the FIGURE 6 position, which they doautomatically, being pushed to this position by the forces of reactionof the well wall thereon when the reamer is moved axially in the wall.

CRITICAL SPACING Referring further to FIGURES 5 'and 6, the radius Rfrom the reamer axis to the tip of any insert is where a is the radiusfrom the reamer axis to the roller axis, b is the radius from the rolleraxis to the tip of the insert, and x is the angle at the intersection ofradius b with radius a. With inserts equally spaced about thecircumference of a roller, the position of overall minimum reamer radiuswill occur when the bisector of the angle between the radius b of twoadjacent inserts is in alignment with radius a. Then with n inserts inthe row, the angle x will be Let U=the underream produced by the subjectreamer R =the radius of an on gage hole, and

R =the reamer radius with an over gage insert aligned with a reamerradius.

Then U=R R The largest amount of underream that can be obtained underthe limitation that the reamer can pass through an on gage hole occurswhen R R and where R is the reamer radius with the bisector of the anglebetween two over gage inserts aligned with a reamer radius. Then, sinceR =(a+b),

so that the larger the value of n the smaller will be U For given valuesof U, a and b, there will be a maximum permissible value of n determinedfrom the above equation. correspondingly there is a minimum value of theinter insert spacing S measured on the roller surface from insert axisto insert axis:

where r is the roller radius at the particular row of inserts. Suchminimum spacing may be referred to in the claims appended hereto as thecritical spacing of the inserts. Combining the last two equations, weobtain the single equation:

The values of r, a and b are immediately apparent on inspection of areamer, and the value of U is determined or indicated in several ways,so that whether or not a reamer roller has its inserts spaced apart noless than the critical spacing is also determined.

DETERMINATION OF UNDERREAM As for the determination of U it may bementioned by way of example that it is usually only slightly less than(b-r) since it is desired to support the inserts with the roller over asmuch of their lengths as possible. It is for this reason that the outerperipheral surface of each roller is preferably stepped. In other words,each insert projects from the roller an amount about equal to themaximum permissible wear contemplated for such insert. In the case ofthe over gage inserts this distance is U.

asoei Assuming that U=br and substituting this value in the lastprevious equation we may then define the critical spacing from theequation:

U may also be determined from the relationship U: i gage since Rgage isthe radius of the on gage hole which is equal to the initial radius ofthe rock bit, and of the reamer at upper land 40 and on-gage bands 46,47 of hard facing. In such case the equation for S the critical spacingbecomes:

1808mm 0 2- R ga e) sm 2 2 since in the position shown min aage This isdesirable so that there will be a slight clearance between the over gageinserts and the hole when the reamer rollers are in position to provideminimum reamer radius at the over gage inserts.

6 t MULTIPLE OVERGAGE INSERT ROWS Referring now to FIGURES 7 and 8 thereis shown a modified form of reamer roller in which there are two rows ofovergage inserts 70, 71, both of the same radius, two rows of on gageinserts 72, 73, and two rows of under gage inserts 74, 75, row 75 beingof smaller radius than row 74. The inserts of equal radius occupy acommon land. 'Ihus, insert rows 70, 71, are on the largest land 76,insert rows 72, 73 are on land 77, insert row 74 is on land 78, andinsert row 75 is on land 79. The bands of hard facing of the firstembodiment have been omitted in this modification in order to provideroom for the extra row of over gage reamer inserts and to permit the useof larger diameter inserts without increasing the roller length.

A further feature of the embodiment of FIGURES 7 and 8 is the use ofsockets for the inserts that do not go all the way through the reamerbody to the bearing sleeve 81. Although this presents additional work toream the sockets 82 to near full diameter at the socket bottoms 83 toenable the inserts to be properly seated therein, bottoming the insertsin the solid body of the reamer provides a firm support for the inserts.The bevel 84 around the bottom periphery of the inserts also facilitatesbottoming of the inserts.

As best shown in FIGURE 9, the inserts in alternate rows of inserts areactually staggered rather than aligned as would appear from FIGURE 7,except that the inserts in over gage rows 70, 71 are in register. Thereare the same number, eight, of inserts in each row, equispaced at 45degrees. Six or eight inserts per row is usual although four to tenmight be used. For the larger diameter tools, preferably larger diameterrollers with more inserts per row are used with the same number ofrollers since three rollers per reamer is so much stronger than a largernumber.

The sleeve and roller body of the FIGURES 7-9 embodiment of theinvention may be made of materials the same as in the first embodimentexcept that the body of the roller is preferably case hardened to about40-45 Rockwell C scale to provide firm support for the inserts at thebottom of the sockets. Although the sockets for the inserts are drilledand reamed after the machined blank has been hardened, it will beobserved that the case hardening of the inside of the roller is of aboutthe thickness of the roller at the socket bottoms.

SLEEVELESS ROLLER Referring now to FIGURE 10 there is shown another formof roller embodying the invention. The roller in this mo'dification'isintegral instead of comprising a body with an internal bushing as in thepreviously described embodiments. This roller, like the bodies of therollers in the previously described embodiment, may be made of a steelsuch as AISI 8620 carburized about one-tenth of an inch deep and casehardened and drawn. However in the absence of any bushing sleeve, theroller of FIGURE 10 is preferably brought to a greater hardness, e.g.,58-62 Rockwell C scale. This construction is less expensive than thecomposite rollers of the previously described embodiments to the extentthat the bushing sleeve is eliminated, and will give satisfactoryservice where the tearing force on the rollers and inserts is not toolarge.

The FIGURE 10 embodiment employs two upper on gage bands 91, 92 of hardfacing material, similar to the first described embodiment. These areprovided in the upper land 93. A row of over gage inserts 94 is providedin land 95; a row of on gage inserts 96 is provided in land 97, and arow of under gage inserts 98 is provided in land 99. Hard facing bands101, 102 corresponding to a reamer radius equal to the minimumpermissible radius of a worn bit are disposed in lower land 103. A hardfacing band 104 is disposed around bevel-led portion 105. Both the upperand lower ends of the roller are provided with further guide bevels at106, 107. Undercut annular areas 110, 111, 112 may be provided 'betweenadjacent lands to insulate the lands from one another to prevent thespreading of metal failure around an insert in one row to the metalaround an insert in an adjacent row.

The operation of the rollers shown in the FIGURES 7-9 and FIGURE 10embodiments is substantially the same as those of the first embodiment,except that in the FIGURES 7-9 embodiment there will be no torque up ofthe drill string upon the reamer or drill bit reaching predetermineddegree of wear since the hard facing bands are omitted in thisembodiment. But the operation of the over gage, on gage, and under gageinserts will be the same in all cases. It will be apparent that it isnot necessary to have any inserts exactly on gage since the reamer reamsover gage until worn to the point of desirable replacement. The on gageinserts are just part of the series of inserts of graduated extents ofprojection leading up to the over gage inserts that bring the hole toits final diameter.

FLATTENED TIPPED INSERTS It will be noted that in FIGURES 7-9 theinserts have been shown as having rounded ends that approximatehemispheres rather than the somewhat blunter shape shown in FIGURES 16and 10. The latter shape is more clearly illustrated in FIGURE 11.Viewed from the top of the reamer as in FIGURE 11, the extreme tip 120of the insert is cylindrical with a radius R going to the reamer axis.This is such a relatively large radius that a fiat will do just about aswell for tip portion 120, the purpose being to provide a large area ofcontact with the well wall that will not wear away too quickly. Theannular portion 121 between tip 120 and the cylindrical surface 122 ofthe body of the insert is spherical with a radius P disposed about .7Pfrom the tip 120 on the insert axis. P is also the radius of thecylindrical surface 122 This spherical area could also be conical, thepurpose being to reduce breakage of the inserts by enabling them towedge against the well wall prior to crushing it rather than striking ita lateral blow. The end shape just described may be called truncated andtogether with the rounded shape shown in FIGURES 710 forms a class ofshapes known as oblate, to be distinguished from shape or pointed.

INCLINED ROLLERS While the invention has been described as applied to areamer having rollers Whose axes are parallel to the reamer axis, itwill be apparent that it is also applicable to reamers whose roller axesare otherwise disposed, e.g., as shown in FIGURE 11 of said Patent2,272,405 with the roller axis coplanar with reamer axis but notparallel thereto, or as shown in FIGURES 12 and 13 of said Patent2,272,405 with the roller axis not coplanar with reamer axis. Since thedistance S determining the critical spacing was measured in a horizontalplane for vertical rollers, obviously reference must be made to thehorizontal component of S when the roller axis is inclined. In caseswhere the roller axes are not parallel to the reamer axis they must atleast have a component of their axes parallel to the reamer axis inorder to cause the rollers to turn as the reamer is rotated about itsaxis. This distinguishes reamer rollers from drill bit rollers or coneswhich contact the bottom of the hole and hence should have at least acomponent of their axes horizontal, i.e., 90 degrees to the vertical. Todraw the distinction more precisely, reamers do not employ rollers whoseaxes make an angle of more than about 30 degrees to the vertical, orotherwise stated, the vertical component is at least 85% of the total.

In the foregoing statement vertical is intended to be synonymous withreamer axis since in normal use the reamer axis is desirably vertical.Thus, if a roller axis is inclined thirty degrees from the vertical, itmakes a thirty degree angle with a line parallel to the reamer axis, andif perpendiculars are dropped from the ends of a unit length of theroller axis onto said line that is parallel to the reamer axis (or thereamer axis itself if coplanar with the roller axis) the perpendicularsWill cut off a portion of the line having a length of 0.866, since thecosine of 30 degrees is 0.866. The orthogonal (perpendicular) projectionof the roller axis on the reamer axis or a line parallel thereto is thus86.6% of the length of the roller axis. In the language of compositionand resolution of vectors, the component of the roller axis that liesparallel to the reamer axis in such case has a length 86.6% of theroller axis length. It is in this sense that in the claims it is saidthat the roller axis must have at least an component parallel to thereamer axis, this being one convenient way of stating the angularposition of the roller axis relative to the reamer axis.

INSERT AXIS AND SECTION Likewise it is to be noted that the tungstencarbide inserts forming the earth formation reducing means of the reamerrollers need not be disposed with the insert axis radial to the rolleraxis, nor need the inserts be of circular cross section, though suchdisposition and shape of the inserts is greatly to be preferred sincethe inserts will be more easily inserted and better retained with thepreferred construction.

The tungsten carbide inserts and the hard facing bands provide means toreduce the earth formation during reaming of the well bore and may bereferred to as such in the appended claims.

While a preferred embodiment of the invention has been shown anddescribed, many modifications thereof can be made by one skilled in theart without departing from the spirit of the invention and it isintended to cover 'by Letters Patent all forms of the invention fallingwithin the scope of the following claims.

We claim:

1. A side wall roller reamer comprising:

a tubular member having means at its upper end for connecting the memberto a rotary drill string whereby the reamer can be rotated about theaxis of said tubular member which thus forms the reamer axis and meansat its lower end for connecting the member to a rotary drill stringwhereby torque and fluid can be transmitted by the reamer from suchdrill string at the upper end of the reamer to such drill string at thelower end of the reamer to rotate a drill bit connected to the lower endof the last mentioned drill string,

a plurality of rollers disposed around the outer periphery of saidtubular member,

means mounting each of said rollers on said member for rotation about anaxis which thus forms the roller axis, said roller axes being parallelto the reamer axis,

each roller having an outer surface that is a surface of revolution withrespect to the roller axis,

each roller being larger in diameter at its upper end than at its lowerend providing an outer surface having portions of increasing radiusprogressing upwards along the roller,

each roller including a plurality of cylindrical apertures in its outersurface disposed around the periphery thereof with their cylindricalaxes perpendicular to the roller axis,

a number of said apertures being disposed in an annular row around eachroller near the upper end thereof,

a generally cylindrical insert disposed in each of said apertures,

each insert including a portion at one end protruding from the apertureand forming a tip adapted to contact the sidewall of a bore hole,

each insert in the apertures below said annular row of aperturesprotruding a distance such that the distance of its tip from the rolleraxis measured perpendicular to the roller axis is at least as great asthe distance from the roller axis of the portion of the outer surface ofthe roller adjacent the aperture nearest thereabove, and

each insert in the apertures in said annular row of apertures equallyprotruding from its aperture to place its tip at a distance (b) from theroller axis, said distance (b) being greater than the maximum distance(r) from the roller axis of the tips of inserts in apertures below saidrow,

the last said distance (1') added to the distance (a) of the roller axisfrom the reamer axis constituting the on-gage radius Rgage of the reameradapted to ream the bore hole to the same radius as the ongage radius ofa new drill bit connected to a drill string below the reamer,

said distance (17) of the tips of the inserts in said annular row fromthe roller axis added to said distance (a) of the roller axis from thereamer axis constituting the underream radius R of the reamer,

each insert in said annular row being disposed with its axis spacedapart from those of the adjacent inserts on both sides thereofprogressing around said row a distance at least equal to the criticalspacing 8 determined by the equation:

2. Method of boring a hole in the earth with a rotary drill stringincluding a drill bit and a side wall roller crusher reamer above thedrill bit having an annular row of oblate tipped crusherscircumferentially spaced apart around each reamer roller a distance Sand whose maximum extension from the reamer axis exceeds the on-gageradius of the drill bit but no more than by a distance U as determinedby the equation:

2 2 a+b cos 1808mm) Where (a) is the radial distance from the rolleraxis to the reamer axis, (r) is the roller radius, and (b) is the radialdistance from the roller axis to the crusher tip, comprising the stepsof lowering the string to the bottom of the hole with the reamer rollersturned to retracted position in which the roller radius bisecting theangle between roller radii to adjacent outermost crushers is alignedwith a reamer radius when the string passes through on-gage portions ofthe hole,

rotating the drill string on bottom to cause the drill bit to borefurther hole and the reamer to underream the previously drilled hole bythe amount said maximum extension of the crusher exceed the ongageradius, and

without rotation of the drill string withdrawing the drill string fromthe hole to cause the oblate tipped crushers to cam the rollers to theaforesaid retracted position.

3. Rotary drilling apparatus including a drill bit adapted to drill anon-ga-ge hole when new and an undergage hole when worn,

a roller crusher reamer above the drill bit adapted to ream the holedrilled by the bit to a diameter in the range of on-gage to overgage,

said reamer including rollers mounted for rotation about axes parallelto the reamer axis,

each roller including an annular row of crusher elements whose maximumprotrusion from the reamer axis is overgage when new,

10 said crusher elements being spaced apart circumferentially about theroller by a distance at least equal to S as determined by the equation:

where R ==on-gage radius of the hole as drilled by the drill bit whennew r=roller radius at the crusher elements a=radius from roller axis toreamer axis b=radius from tips of crusher elements to roller axis.

4. A roller ream-er including a tubular body with a plurality of rollersmounted thereon for rotation about axes parallel to the body axis, eachroller having earth formation reducing elements radially protrudingtherefrom and circumferentially spaced apart about the roller at least adistance S determined by the equation:

rzroller radius a=radius from roller axis to axis of tubular bodyb=radius from roller axis to tip of element.

5. An underreamer comprising a tubular body having a plurality ofrollers rotatably mounted thereon for rotation parallel to the bodyaxis, each roller having elements protruding therefrom adapted tounderream by a radial distance U, the elements being circumferentiallyspaced about the roller by a distance at least equal to S as determinedby the equation:

2 2 (a b cos 1808mm) where a is the radial distance from the roller axisto the body axis; r is the roller radius; and b is the radial distancefrom the roller axis to the tip of the element. 6. An underreamercomprising a tubular body having a plurality of rollers rotatablymounted thereon for rotation about axes having at least an componentparallel to the body axis, the upper end of each roller axis being atleast as far from the reamer axis as the lower end thereof, each rollerhaving elements protruding therefrom adapted to underream by a radialdistance U, the elements being circumferentially spaced apart about theroller by a distance whose component in a plane perpendicular to thebody axis is at least equal to 8 as determined by the equation:

where a is the radial distance from the roller axis to the body axis; ris the roller radius; and b is the radial distance from the roller axisto the tip of the element. 7. Well apparatus for reaming a holefollowing a drill bit to maintain the hole at least full gage asdrilling progresses and the initially full gage drill bit wearsundergage comprising an underreamer in accordance with claim 6, means atthe upper and lower ends of the underreamer body for connecting the bodyin a rotary drill string whereby the body can be rotated about the axisof the body collinear with the drill string axis, and means comprisingoblate outer tips on the protruding underream elements of theunderreamer rollers to cam the rollers into positions in which themi-dpoints between the elements nearest the underreamer outer peripheryare coplanar with the body axis and the respective roller axis when saidapparatus is moved 1 1 axially into a full gage portion of a holewithout retating said apparatus about said body axis,

the radii from the extremeties of the underream elernents to the bodyaxis being no greater than said full gage when said rollers are in saidposition, due to said spacing of at least S between said elements.

8. A reamer comprising a tubular member having means at its upper andlower a plurality of rollers disposed around the outer periphery of saidtubular member, means rotatably mounting each of said rollers on saidtubular member with its roller axis having at least an 85% componentparallel to the reamer axis, each roller being of progressivelyincreasing diametens all the way from adjacent the lower end to adjacentthe upper end of the reamer, the diameter increasing stepwise along thelength of the roller forming a plurality of annular lands each ofuniform diameter, there being an annular band of radial socketsextending around each land, the sockets having sides that are straightin the direction progressing inwardly from the outer surface of theroller,

earth formation reducing means at the outer peripheral surface of eachroller, said earth formation reducing means comprising a plurality oftungsten carbide inserts disposed in annular bands in said sockets inthe roller lands, each insert having a straight sided root portionmaking an interference fit within its socket and an oblate tip portionextending out of the socket, the tips of the inserts disposed in eachlarger radius land extending farther from the roller axis than the tipsof the inserts in the next smaller radi-us land, the tips of the insertsin each land protruding therefrom to a distance at least as far from theroller axis as the periphery of the next larger land,

said earth formation reducing means further including an annularbevelled area adjacent the smallest diameter land, said bevelled areabeing provided with a band of hard facing material therearound, saidbevelled area having an annular groove thereon receiving said hardfacing whereby the latter is flush with the surface of said area.

9. A reamer comprising a tubular member having means at 1ts upper andlower a plurality of rollers disposed around the outer periphery of saidtubular member, means rotatably mounting each of said rollers on saidtubular member with its roller axis having at least an 85% componentparallel to the reamer axis, each roller being of progressivelyincreasing diameters all the way from adjacent the lower end to adjacentthe upper end of the reamer, the diameter increasing stepwise along thelength of the roller forming a plurality of annular lands each ofuniform diameter, there being an annular band of radial socketsextending around each land, the sockets having sides that are straightin the direction progressing inwardly from the outer surface of theroller,

earth formation reducing means at the outer peripheral surface of eachroller, said earth formation reducing means comprising a plurality oftungsten carbide inserts disposed in annular bands in said sockets inthe roller lands, each insert having a straight sided root portionmaking an interference fit within its socket and an oblate tip portionextending out of the socket, the tips of the inserts disposed 12 in eachlarger radius land extending farther from the roller axis than the tipsof the inserts in the next smaller radius land, the tips of the insertsin each land protruding therefrom to a distance at least as far from theroller axis as the periphery of the next larger land,

said earth formation reducing means further including an annular band ofhard facing material around the roller at the end thereof adjacent thesmallest diameter land, the maximum radial extent of said hard facingfrom the reamer axis being a predetermined amount less than the on-gageradius of the hole to be reamed, whereby when the bit on the drillstring has worn down to said predetermined amount below full gage saidhard facing band will cause torque up of the drill string.

19. A reamer comprising a tubular member having means at its upper andlower ends for connecting the member in a rotary drill string wherebythe reamer can be rotated about the axis of said tubular member whichthus forms the reamer axis,

a plurality of rollers disposed around the outer periphery of saidtubular member, means rotatably mount ing each of said rollers on saidtubular member with its roller axis having at least an componentparallel to the reamer axis, each roller being of progressivelyincreasing diameters all the way from adjacent the lower end to adjacentthe upper end of the reamer, the diameter increasing stepwise along thelength of the roller forming a plurality of annular lands each ofuniform diameter, there being an annular band of radial socketsextending around each land, the sockets having sides that are straightin the direction progressing inwardly from the outer surface of theroller,

earth formation reducing means at the outer peripheral surface of eachroller, said earth formation reducing means comprising a plurality oftungsten carbide inserts disposed in annular bands in said sockets inthe roller lands, each insert having a straight sided root portionmaking an interference fit within its socket and an oblate tip portionextending out of the socket, the tips of the inserts disposed in eachlarger radius land extending farther from the roller axis than the tipsof the inserts in the next smaller radius land, the tips of the insertsin each land protruding therefrom to a distance at least as far from theroller axis as the periphery of the next larger land,

said means rotatably mounting each roller including a sleeve bushinginside the roller, said bushing being harder than the outer part of theroller, the outer part of the roller being more ductile than saidbushing in order better to retain said inserts,

said openings in the roller extending all the way inwardly to saidbushing and said inserts being bottomed against said bushing.

11. A reamer comprising a tubular member having means at its upper andlower ends for connecting the member in a rotary drill string wherebythe reamer can be rotated about the axis of said tubular member whichthus forms the reamer axis,

a plurality of rollers disposed around the outer periphery of saidtubular member, means rotatably mounting each of said rollers on saidtubular member with its roller axis having at least an 85% componentparallel to the reamer axis, each roller being of progressivelyincreasing diameters all the way from adjacent the lower end to adjacentthe upper end of the reamer, the diameter increasing stepwise along thelength of the roller forming a plurality of annular lands each ofuniform diameter, there being an annular band of radial socketsextendingaround each land, the sockets having sides that are straight in thedirection progressing inwardly from the outer surface of the roller,

earth formation reducing means at the outer peripheral surface of eachroller, said earth formation reducing means comprising a plurality oftungsten carbide inserts disposed in annular bands in said sockets inthe roller lands, each insert having a straight sided root portionmaking an interference fit within its socket and an oblate tip portionextending out of the socket, the tips of the inserts disposed in eachlarger radius land extending farther from the roller axis than the tipsof the inserts in the next smaller radius land, the tips of the insertsin each land protruding therefrom to a distance at least as far from theroller axis as the periphery of the next larger land,

said earth formation reducing means further including an annular band ofhard facing material around the roller at the upper end thereof, themaximum radial extent of said hard facing from the reamer axis being theon gage radius of the reamer, inserts in the uppermost land of eachroller having a maximum radial extent greater than said on gage radiusso as to ream an overgage hole, said on gage 'band of hard facingserving to burnish the hole afterthe action of the inserts, said on gageband further serving to cause torque-up of the drill string when theovergage inserts are worn down to on-gage.

12. The combination of claim 11 in which the peripheral distance betweenthe overgage inserts measured about the roller surface is at least equalto the critical spacing allowing the rollers to "be turned intopositions in which none of the overgage inserts extends radially fromthe reamer axis more than the on gage radius of the reamer.

13. The combination of claim 12 in which said overgage bits are disposedin a plurality of annular rows around the roller and the bits in one roware in register with those in an adjacent row.

14. A reamer comprising a tubular member having means at its upper andlower ends for connecting the member in a rotary drill string wherebythe reamer can be rotated about the axis of said tubular member whichthus forms the reamer axis,

a plurality of rollers disposed around the outer periphery of saidtubular member, means rotatably mounting each of said rollers on saidtubular member with its roller axis parallel to the reamer axis,

each roller being of progressively increasing diameters all the way fromadjacent the lower end to adjacent the upper end of the reamer, thediameter increasing stepwise along the length of the roller forming aplurality of annular lands each of uniform diameter,

there being an annular 'band of radial sockets extending around eachland, the sockets having sides that are straight in the directionprogressing inwardly from the outer surface of the roller,

earth formation reducing means at the outer peripheral surface of eachroller, said earth formation reducing means comprising a plurality oftungsten carbide inserts disposed in annular bands in said sockets inthe roller lands, each insert having a straight sided root portionmaking an interference fit within its socket and an oblate tip portionextending out of the socket, the tips of the inserts disposed in eachlarger radius land extending farther from the roller axis than the tipsof the inserts in the next smaller radius land, the tips of the insertsin each land protruding therefrom to a distance at least as far from theroller axis as the periphery of the next larger land,

said sockets in said land.and said inserts therein having cylindricalsides with the cylinder axis radial to the axis of the respectiverollers and uniformly spaced apart circumferentially around the rollers,the sockets and inserts in one land being staggered relative to those inan adjacent land,

said sockets terminating within each roller at points spaced radiallyoutward from said means rotatably mounting the rollers on said tubularmember so as to provide a solid bottom for each socket.

References Cited by the Examiner UNITED STATES PATENTS 1,747,909 2/1930Seifert -318 2,094,855 10/1937 Smith 175-346 2,121,202 6/1938 Killgore175- 74 2,187,037 1/1940 Kirkpatrick 175-335 2,222,818 11/1940 Koppl175-347 2,272,405 2/ 1942 Grant et al. 175-346 2,687,875 8/1954 Morlanet al 175-374 2,689,108 9/1954 Haglund 175-411 CHARLES E. OCONNELL,Primary Examiner. I. A. LEPPINK, Assistant Examiner,

1. A SIDE WALL ROLLER REAMER COMPRISING: A TUBULAR MEMBER HAVING MEANSAT ITS UPPER END FOR CONNECTING THE MEMBER TO A ROTARY DRILL STRINGWHEREBY THE REAMER CAN BE ROTATED ABOUT THE AXIS OF SAID TUBULAR MEMBERWHICH THUS FORMS THE REAMER AXIS AND MEANS AT ITS LOWER END FORCONNECTING THE MEMBER TO A ROTARY DRILL STRING WHEREBY TORQUE AND FLUIDCAN BE TRANSMITTED BY THE REAMER FROM SUCH DRILL STRING AT THE UPPER ENDOF THE REAMER TO SUCH DRILL STRING AT THE LOWER END OF THE REAMER TOROTATE A DRILL BIT CONNECTED TO THE LOWER END OF THE LAST MENTIONEDDRILL STRING, A PLURALITY OF ROLLERS DISPOSED AROUND THE OUTER PERIPHERYOF SAID TUBULAR MEMBER, MEANS MOUNTING EACH OF SAID ROLLERS ON SAIDMEMBER FOR ROTATION ABOUT AN AXIS WHICH THUS FORMS THE ROLLER AXIS, SAIDROLLER AXES BEING PARALLEL TO THE REAMER AXIS, EACH ROLLER HAVING ANOUTER SURFACE THAT IS A SURFACE OF REVOLUTION WITH RESPECT TO THE ROLLERAXIS, EACH ROLLER BEING LARGER IN DIAMETER AT ITS UPPER END THAN AT ITSLOWER END PROVIDING AN OUTER SURFACE HAVING PORTIONS OF INCREASINGRADIUS PROGRESSING UPWARDS ALONG THE ROLLER, EACH ROLLER INCLUDING APLURALITY OF CYLINDRICAL APERTURES IN ITS OUTER SURFACE DISPOSED AROUNDTHE PERIPHERY THEREOF WITH THEIR CYLINDRICAL AXES PERPENDICULAR TO THEROLLER AXIS, A NUMBER OF SAID APERTURES BEING DISPOSED IN AN ANNULAR ROWAROUND EACH ROLLER NEAR THE UPPER END THEREOF, A GENERALLY CYLINDRICALINSERT DISPOSED IN EACH OF SAID APERTURES, EACH INSERT INCLUDING APORTION AT ONE END PROTRUDING FROM THE APERTURE AND FORMING A TIPADAPTED TO CONTACT THE SIDEWALL OF A BORE HOLE, EACH INSERT IN THEAPERTURES BELOW SAID ANNULAR ROW OF APERTURES PROTRUDING A DISTANCE SUCHTHAT THE DISTANCE OF ITS TIP FROM THE ROLLER AXIS MEASURED PERPENDICULARTO THE ROLLER AXIS IS AT LEAST AS GREAT AS THE DISTANCE FROM THE ROLLERAXIS OF THE PORTION OF THE OUTER SURFACE OF THE ROLLER ADJACENT THEAPERTURE NEAREST THEREABOVE, AND EACH INSERT IN THE APERTURES IN SAIDANNULAR ROW OF APERTURES EQUALLY PROTRUDING FROM ITS APERTURE TO PLACEITS TIP AT A DISTANCE (B) FROM THE ROLLER AXIS, SAID DISTANCE (B) BEINGGREATER THAN THE MAXIMUM DISTANCE (R) FROM THE ROLLER AXIS OF THE TIPSOF INSERTS IN APERTURES BELOW SAID ROW, THE LAST SAID DISTANCE (R) ADDEDTO THE DISTANCE (A) OF THE ROLLER AXIS FROM THE REAMER AXIS CONSTITUTINGTHE ON-GAGE RADIUS RGAGE OF THE REAMER ADAPTED TO REAM THE BORE HOLE TOTHE SAME RADIUS AS THE ONGAGE RADIUS OF A NEW DRILL BIT CONNECTED TO ADRILL STRING BELOW THE REAMER,